The invention relates to a combination filter assembly having a number of filter elements that are arranged in parallel one after the other in the direction of flow, wherein each of the filter elements typically comprises a filter sieve that is stretched across and mounted to a housing element. The combination filter assembly is formed by stacking the housing elements one on top of the other.
Combination filter assemblies of this kind are generally known, and apart from other possible uses, are most often used in the cosmetic and pharmaceutic industry to produce a foam from chemical fluids. To this end, the chemical fluid is forced, by the pressure of an inert gas or air, through a combination filter assembly having two to four extremely fine filter sieves. The sieves are arranged in a parallel, stacked formation, and typically have an interior diameter of between 6 and 10 mm, with a mesh size in the range 40 and 50 Micron. The size of the bubbles of the foam produced by the filter is determined by the mesh size of the sieves.
The combination filter assembly typically consists of a cylindrical housing of plastic having an inlet section and an outlet section, wherein the cylindrical filter elements are stacked and inserted into the housing with their annular bearing faces contacting each other. This arrangement, however, has a number of disadvantages. For example, bypasses or leaks can occur between the individual filter sieves, thereby allowing the chemical fluid to bypass the filter sieves. This can result in the formation of a foam having uncontrolled and non-uniform sizes of bubbles, thereby producing a foam of reduced quality of the foam.